Small form factor power supply

Abstract

A new, small form factor power supply is disclosed that provides a regulated DC power supply in a package that radiates relatively little heat and that occupies 2.75" by 4.5" by 0.75". The secondary coil of the transformer is positioned at the summing node of the flux of the primary coils and the phase of the drive signals provided to the secondary coils is regulated to control the current and voltage provided by the secondary circuit. Preferably, all circuit components are surface mount devices and the transformer cores are E block planar cores mounted on the printed circuit board.

I claim: 
     
       1. A power supply circuit, the circuit comprising: a magnetic core;   first and second primary coals electromagnetically coupled to the core to induce magnetic flux in the core; and   a secondary coil electromagnetically coupled to the core to generate an electromotive force based upon the magnetic flux in the core, wherein the secondary coil is positioned relative to the primary coils such that the flux generated by the primary coils constructively interfere;   driving circuitry coupled to each of the primary coils to provide a separate driving signal to each primary coil and each driving signal having a phase a phase relationship existing between the driving signals;   a rectifier coupled to the secondary coil to provide a regulated DC signal and   a feedback means coupled between the output of the rectifier and the driving circuitry to alter the phase relationship between the driving signals to regulate the DC signal.   
     
     
       2. The power supply circuit of claim 1, wherein the feedback means includes: a current sensing circuit coupled to the secondary coil to sense current flow through the secondary coil;   a voltage sensing circuit coupled to the regulated DC signal;   an amplitude modulation circuit to amplitude modulate a signal based upon the sensed voltage and current flow; and   a feedback transformer coupled to the amplitude modulation circuit.   
     
     
       3. The power supply circuit of claim 1, wherein the core is an E block type and each primary coil is mounted on an outer leg of the core and the secondary coil is mounted on an inner leg. 
     
     
       4. The power supply circuit of claim 2, wherein the core is an E block type and each primary coil is mounted on an outer leg of the core and the secondary coil is mounted on an inner leg of the core. 
     
     
       5. The power supply circuit of claim 1, wherein the core is a low profile magnetic core. 
     
     
       6. A method for providing a regulated power supply providing a regulated direct current output signal having at least one parameter at a predefined level, the method comprising: providing a first and second driving signal each having a phase, a controllable phase relationship existing between the signals;   providing a first magnetic core with a plurality of primary coils magnetically coupled to the core to produce magnetic flux therein and at least a secondary coil magnetically coupled to the core such that the secondary coil is positioned at a point where the magnetic flux from the two primary coils constructively interfere so that the secondary coil has a current induced therein when the primary coils are driven;   providing the direct current output signal based upon the current induced in the secondary coil,   sensing at least one parameter of the output signal;   providing a feedback signal based upon the sensed parameter; and   altering the controllable phase relationship exists between the driving signals to keep the parameter of the output signal within a predetermine range of the level.   
     
     
       7. The method of claim 6, wherein the parameter is current. 
     
     
       8. The method of claim 6, wherein the parameter is voltage. 
     
     
       9. The method of claim 6, wherein each primary coil is part of a separate resonant circuit. 
     
     
       10. The method of claim 9, wherein the frequencies of the drive signals are substantially at the resonant frequency of the resonant circuit. 
     
     
       11. The method of claim 6, wherein the providing of the feedback signal comprises: inducing a feedback current based upon the magnetic flux induced in the core; and   amplitude modulating the feedback current based upon the parameter.   
     
     
       12. A power supply circuit, the circuit comprising: a magnetic core;   first and second primary coils electromagnetically coupled to the core to induce magnetic flux in the core; and   a secondary coil electromagnetically coupled to the core to generate an electromotive force based upon the magnetic flux in the core, wherein the secondary coil is positioned relative to the primary coils such that the flux generated by the primary coils destructively interfere:   driving circuitry coupled to each of the primary coils to provide a separate driving signal to each primary coil and each driving signal having a phase, a phase relationship existing between the driving signals;   a rectifier coupled to the secondary coil to provide a regulated DC signal; and   a feedback means coupled between the output of the rectifier and the driving circuitry to alter the phase relationship between the driving signals to regulate the DC signal.